Fairing for a combustion chamber end wall

Abstract

An annular fairing for covering the annular chamber end wall of a turbomachine combustion chamber, and in particular of an airplane turbojet. The fairing presents openings for passing fuel injectors that are supported by the chamber end wall. The fairing is subdivided into a plurality of adjacent sectors, each sector presenting inner and outer fastener edges capable of being fastened on either side of said chamber end wall. Each sector includes a lip on one of its side edges, which lip is connected to the remainder of the sector by a step, said lip being designed to over the side edge of the adjacent sector.

Description

[0001]The present invention relates to an annular fairing for covering the annular end wall of a turbomachine combustion chamber. The invention is applicable to any type of terrestrial or aviation turbomachine, and more particularly to airplane turbojets.BACKGROUND OF THE INVENTION[0002]Conventional turbojet combustion chambers comprise an inner wall, an outer wall, and in the upstream region of the chamber, an annular end wall disposed between said inner and outer walls. The chamber end wall supports injector heads that spray fuel into the combustion chamber.[0003]Those conventional combustion chambers also have an annular fairing serving firstly to cover the upstream (i.e. front) end of said chamber end wall together with said injector heads so as to protect them from any impact (as can occur if a bird or a block of ice is ingested into the turbojet), and secondly to ensure that the chamber end wall is aerodynamically contoured allowing air to flow with little head loss.[0004]In t...

AI Technical Summary

Benefits of technology

[0012]The fairing of the invention is fastened sector by sector onto the upstream edges of the outer and inner walls of the combustion chamber, thus making it possible to avoid forming the above-mentioned deformation lobes and to guarantee good contact between the fastener edges of each sector and said walls. In addition, there is no need to provide slots in the fastener edges, thereby avoiding the drawbacks associated with the presence of such slots.

[0013]In addition, with known fairings (as explained above), part of the bolt clamping force is used for deforming the fairing which is rigid. Since the fairing sectors of the invention are more flexible, it is possible either to reduce the clamping force, or else to obtain better contact between the assembled-together parts for the same clamping force.

[0015]By means of such overlap, air leakage between two adjacent sectors is avoided.

[0018]Said N-1 oblong holes extend in the circumferential direction of the fairing, and the holes enable said fastener elements to move circumferentially during mounting, such movement being due to the radial approach of the fairing to the diameters of the outer, inner, and end walls of the combustion chamber. This enables better contact and thus more effective clamping in the assembly, and avoids generating stresses in the sectors.

[0020]Having a single fastening point per fastener edge avoids problems associated with expansion differences between the assembled-together parts, in the event of such expansion differences being large while the turbomachine is in operation. In addition, since said fastening points are generally provided by means of a fastener element, in particular a bolt, passing through a hole formed in the sector, reducing the number of fastening points as much as possible reduces the number of fastener elements (bolts) that are used, thereby achieving a saving in weight. There is also a reduction in the number of holes to be made and thus in the cost of fabricating each sector. In addition, since the side edges of two adjacent sectors overlap, a sector contributes to holding in place the adjacent sector that it overlaps. Finally, as described below, the operation of fastening the sectors on the outer, inner, and end walls of the chamber remains simple.

Problems solved by technology

During this step, the bolt needs to be tightened quite considerably in order to take up assembly clearances that are inherent to fabrication and mounting tolerances, and that has the drawback of causing the fairing to lose its annular shape, the inner and / or outer edges of the fairing forming deformation lobes between pairs of bolts, giving these edges a “daisy” shape.

These lobes cause gaps to appear between the assembled parts, giving rise to air leakage and head losses.

In addition, given said mounting clearances, the mechanical stiffness of the assembly leads either to tightening with torque that is greater than can be accommodated by the bolt and / or the fairing, or else to insufficient contact for friction to pass operating forces via the bolted connections.

Nevertheless, that solution presents other drawbacks: in operation the slots lead to leaks of air that are harmful from an aerodynamic point of view and they also run the risk of constituting crack initiation points.

Images